ISOTOPIC SPIKES FROM TROPICAL CYCLONES IN SURFACE WATERS - OPPORTUNITIES IN HYDROLOGY AND PALEOCLIMATOLOGY

The stable isotopic ratio of precipitation from tropical cyclones is v ery low compared to that of normal summer precipitation (Lawrence and Gedzelman, 1996). Tropical Storms Allison and Chantal made landfall in southeast Texas in the summer of 1989 and dumped large amounts of rai n. Isotope ratios of surface waters measured at five different sites d ecreased markedly after the passage and remained low for a Pew weeks. The return of isotope values to normalcy following these storms varied from site to site reflecting differences among the hydrological envir onments. During other summers from 1985 to 1993 isotope ratios of rain s were higher and in the normal range. Calculations using air temperat ures and oxygen isotope measurements of the surface waters show that o rganically precipitated fresh water carbonate should have recorded the two oxygen isotopic spikes produced by Allison and Chantal at all fiv e sites, This suggests that isotopic analysis of ancient fresh water f ossil carbonate shells, fossil mammal teeth or tree rings might be use d to document past tropical cyclone activity. (C) 1998 Elsevier Scienc e B.V.